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  Adjustable illumination blade assembly for photolithography scannersUSPTO Application #: 20060103828Title: Adjustable illumination blade assembly for photolithography scanners Abstract: A method and structure for providing adjustable optical lithography illumination comprises a blade which can be customized to provide a desired light pattern. The adjustable blade can be selectively configured to optimize a light pattern during development of a photolithographic process, then the optimized pattern can be transferred to a diffractive optical element or other light shaping means for production. Descriptions and depictions of specific adjustable blades are provided. (end of abstract)
Agent: Kevin D. Martin Micron Technology, Inc. - Boise, ID, US Inventor: Douglas J. David USPTO Applicaton #: 20060103828 - Class: 355067000 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20060103828. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] This invention relates to the field of semiconductor manufacture and, more particularly, to photolithography equipment useful during the formation of a semiconductor device. BACKGROUND OF THE INVENTION [0002] During the formation of a semiconductor device many features such as conductors (word lines, digit lines), electrical contacts, and other physical features are commonly formed from, into, and over a semiconductor wafer. A goal of semiconductor device engineers is to form as many of these features in a given area as possible to increase yield percentages and to decrease device size and manufacturing costs. [0003] All heterogeneous structures on a semiconductor wafer requires lithography. Optical lithography, the lithographic method most used in leading-edge wafer processing, comprises projecting coherent light of a given wavelength from an illumination source (illuminator) through a quartz photomask or reticle having a chrome pattern thereon, and imaging that pattern onto a photoresist-coated wafer. The light chemically alters the photoactive photoresist and allows the exposed photoresist (if positive resist is used) or the unexposed photoresist (if negative resist is used) to be rinsed away using a developer. [0004] With decreasing feature sizes the limits of optical lithography are continually being tested and lithographic methods and materials are continually being improved through various developments, generally referred to as resolution enhancement techniques (RET's). RET's alter various aspects of the lithographic process to optimize the size and shape of a desired feature. For example, the wavelength of light used to expose the photoresist may be decreased, as longer wavelengths cannot resolve the decreasing feature sizes. The wavelength used with lithographic equipment has decreased from 365 nanometers (nm) in the mid-1980's to the current standard of 193 nm. Another RET includes optical proximity correction, which uses subresolution changes in the chrome pattern on the photomask or reticle to optimize the shape of the light focused on the photoresist. Without optical proximity correction, the chrome pattern is a scaled shape of the pattern which is to be produced. With very small features a scaled shape does not produce the desired pattern due to diffraction effects. However, the chrome photomask features can be modified in a manner that attempts to account for these diffraction effects. U.S. Pat. No. 6,245,468 by Futrell et al., assigned to Micron Technology, Inc. and incorporated herein by reference as if set forth in its entirety, describes an optical proximity correction apparatus and method. A third RET uses unequal photomask thickness of the quartz on which the chrome is formed at selected locations between the chrome to provide a phase-shift photomask. Phase shifting sets up destructive interference between adjacent light waves to enhance the pattern formed on the photoresist. [0005] Another resolution enhancement technique is off-axis illumination, which improves the resolution of repeating patterns found in semiconductor device manufacture. FIG. 1 depicts an apparatus comprising off-axis illumination, and depicts an illuminator 10 comprising a laser which provides a coherent light source 12, a diffractive optical element (DOE) 14, a zoom axicon 16, a first reflector 18, a blade 20, an optical homogenizer 22, a second reflector 24, a vertical photomask 26, a lens 28, and a wafer 30 comprising a layer of photoresist (not individually depicted). It should be noted that the simultaneous use of a blade 20 and a DOE 14 as depicted in FIG. 1 is for illustration purposes only, as the use of one typically excludes the use of the other. A structure similar to the one depicted in FIG. 1, as well as the other RET's previous listed, are described and illustrated in A Little Light Magic, IEEE Spectrum, September 2003, pp. 34-39. [0006] During research and development of a production process, simulation software is often used to predict the accuracy of an optical pattern for use with an illumination source on a stepper or scanner. As with circuit simulation, this software closely emulates the actual output which will be produced, but is not an exact representation and some trial and error manipulation of patterns is often necessary. To tune the illumination source pattern, a number of blades having different fixed patterns are used. In operation, each fixed blade is sequentially and manually inserted into the illumination path by a technician or engineer to determine the best illumination pattern for the mask or reticle being used. Changing a blade requires the engineer to first idle the equipment, manually replace the blade, initialize and calibrate the equipment, then return the tool to production. DOE's may also be used to determine a workable pattern and in fact function better than blades because they do not limit illumination intensity and can be placed into the light path by the equipment itself, however they are very expensive and have a construction lead time of several weeks. In practice, blades are used to determine the best pattern, then a DOE having the correct pattern based on testing using blades is ordered and used in production. [0007] A method and structure for decreasing the time and expense of selecting a suitable DOE pattern during research and development of a production photolithography process would be desirable. SUMMARY OF THE INVENTION [0008] The present invention provides a new method and apparatus which, among other advantages, decreases the time and expense required to select a suitable diffused optical element pattern during the research and development of a photolithography process to form a semiconductor device. In accordance with one embodiment of the invention, an adjustable blade mechanism is used which may be adjusted remotely through equipment software. This eliminates the requirement for manual replacement of one blade with another by an engineer or technician. [0009] Advantages will become apparent to those skilled in the art from the following detailed description read in conjunction with the appended claims and the drawings attached hereto. BRIEF DESCRIPTION OF THE DRAWINGS [0010] FIG. 1 depicts a conventional optical lithography apparatus; [0011] FIG. 2 depicts a computer controller connected to an adjustable optical lithography blade apparatus; [0012] FIG. 3 depicts a front view of a first embodiment of an adjustable blade apparatus; [0013] FIG. 4 is an isometric view of the blade arms and gears for adjusting the arms; [0014] FIG. 5 is an embodiment of a frame to which the arms of the blade are mounted; [0015] FIG. 6 is a side view, and FIG. 7 is a front view, of another embodiment of the blade apparatus having arms which are adjustable using electromagnets; [0016] FIG. 8 is a front view of a quadrupole blade apparatus; [0017] FIG. 9 is a front view of an annulus blade apparatus; [0018] FIG. 10 is an isometric depiction of various components which may be manufactured using devices formed using an embodiment of the present invention; and [0019] FIG. 11 is a block diagram of an exemplary use of the invention to form part of a transistor array in a memory device. [0020] It should be emphasized that the drawings herein may not be to exact scale and are schematic representations. The drawings are not intended to portray the specific parameters, materials, particular uses, or the structural details of the invention, which can be determined by one of skill in the art by examination of the information herein. Continue reading... Full patent description for Adjustable illumination blade assembly for photolithography scanners Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Adjustable illumination blade assembly for photolithography scanners patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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